netdev - Re: [PATCH bpf-next v2 2/4] xsk: add proper barriers and {READ, WRITE}

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Date:   Mon, 26 Aug 2019 10:57:53 -0700
From:   "Jonathan Lemon" <jonathan.lemon@...il.com>
To:     "Björn Töpel" <bjorn.topel@...el.com>
Cc:     "Ilya Maximets" <i.maximets@...sung.com>,
        "Björn Töpel" <bjorn.topel@...il.com>,
        ast@...nel.org, daniel@...earbox.net, netdev@...r.kernel.org,
        magnus.karlsson@...el.com, magnus.karlsson@...il.com,
        bpf@...r.kernel.org,
        syzbot+c82697e3043781e08802@...kaller.appspotmail.com,
        hdanton@...a.com
Subject: Re: [PATCH bpf-next v2 2/4] xsk: add proper barriers and {READ,
 WRITE}_ONCE-correctness for state



On 26 Aug 2019, at 9:34, Björn Töpel wrote:

> On 2019-08-26 17:24, Ilya Maximets wrote:
>> This changes the error code a bit.
>> Previously:
>>     umem exists + xs unbound    --> EINVAL
>>     no umem     + xs unbound    --> EBADF
>>     xs bound to different dev/q --> EINVAL
>>
>> With this change:
>>     umem exists + xs unbound    --> EBADF
>>     no umem     + xs unbound    --> EBADF
>>     xs bound to different dev/q --> EINVAL
>>
>> Just a note. Not sure if this is important.
>>
>
> Note that this is for *shared* umem, so it's very seldom used. Still,
> you're right, that strictly this is an uapi break, but I'd vote for the
> change still. I find it hard to see that anyone relies on EINVAL/EBADF
> for shared umem bind.
>
> Opinions? :-)

I'd agree - if it isn't documented somewhere, it's not an API break. :)
-- 
Jonathan